1. Field of the Invention
The present invention relates to semiconductor processing. More particularly, the present invention relates to clamp rings for securing a work piece or substrate in a processing chamber.
2. Background of the Related Art
In the manufacturer of integrated circuits and other electronic devices, multiple layers of dielectric, conducting, and semiconducting materials are deposited and etched from the surface of substrates. Typically, substrates are positioned within vacuum processing chambers where plasma reactions are performed to either deposit material on the substrate or etch material from the substrate. In order to protect the edge of substrates and to secure substrates to the support member during processing, clamp rings are sometimes used to contact the edge of the substrate during processing. After many hours of operation, typically hundreds of hours, the upper surfaces of the clamp ring can be eroded by etching processes or can collect deposition material in deposition processes. As a result, the clamp ring must be replaced.
FIG. 1 is a perspective view of one type of clamp ring used in the field. The clamp ring 100 generally includes downwardly extending flanges 102 that protect portions of a processing chamber in an etching process. The clamp ring also includes tabs 104, otherwise known as "fingers", that engage the edge of a substrate 24 positioned on a support member, such as a pedestal, in a processing chamber. The tabs 104 extend radially inward of the clamp ring and are used to hold the substrate during processing. The clamp ring is mounted on a lift mechanism in the chamber by inserting a fastener, such as a screw, through a hole 108 and a counterbore 106. A cap 110 may be used to cover the fastener and protect the fastener from the etching process. The upper surface 112 of the clamp ring is exposed primarily to the etching process and erodes from continued use and must eventually be replaced.
Unfortunately, in some processes the material from which the clamp ring is made is very expensive. As one example, a VESPEL.RTM. clamp ring is typically used in some etching processes. The clamp ring includes not only a shielding and clamping portion, but also an annular ring portion which serves as a support for the clamp ring and/or as a shield. Difficult machining also adds cost to the clamp ring.
Therefore, there is a need for a clamp ring which can be easily replaced and which does not require difficult machining.